Stainless Steel Prop

S

Swee Pea

New member
Just replaced my "Honda" stock aluminum 13.5x15 prop with a Michigan Match stainless steel prop 13.75x15. I could not resist the price - $169.00. Such a deal. Will hopefully take Swee Pea out in the next week or so and see if I notice any difference. Probably not. Anyone have any experience with the Michigan Match line of props?

John
Swee Pea
 
In theory, in the event of a prop strike, the hub should spin before doing damage to the lower end, right?

Does anybody here have any first hand experience with a prop strike damaging a lower unit?

Was just wondering how real the risk is when running a SS prop.
 
I have an 03' NOS Yami 75f. I hit a gravel bar last summer and ruined my aluminum prop. When I went to put on the new one I noticed that the propshaft was bent :cry . (600.00 repair bill). I would never count on the "hub spinning" to save anything. Here's a pic.

CIMG0513.sized.jpg
 
AK Angler":266vlwa1 said:
the hub should spin before doing damage to the lower end, right?
Click to expand...

On my Honda 45's, the prop is on a splined shaft (horizontal) which is hooked to a pinion gear that mates to another pinion gear that is hooked to the drive shaft (vertical). I don't see anything that will "spin" or prevent damage to the whole unit should the prop suddenly stop. I would think that the aluminum prop would come apart a lot quicker than the SS one. It would be pretty hard to get something that big past the skeg/lower unit front end though, unless you were backing!! :smileo

Older engines, smaller ones, had shear pins in them that would break before anything else but I don't think the big new ones do.

My lower unit damage was caused by getting fishing line wrapped around the shaft between the prop and the housing. DSCN1543.sized.jpg

I'm in the process of replacing the whole lower unit with one from Halcyon's blown 40HP engine. The remainder of the engine will be available for parts to C-Brats on a no cost basis (shipping only). Will post that opportunity separately when I get the engine. Parts should be common to 35/40/45/50HP Hondas.

Charlie
 
To the best of my knowledge, most outboard props have rubber in them between the prop itself and the inner splined section. Very small outboards just have a shearpin. I've had hubs spin in the past but it was on older outboards. Maybe they don't do it that way anymore. I guess I'll look at my Honda tonight.
I've always questioned whether an aluminum prop would be better than stainless during a prop-strike. Aluminum props are pretty tough. I'm sure fiber props would prevent lower unit damage.
 
The "hub" folks are referring to is the bushing inside the prop. See part #13 in this PDF of the prop on my Suzis:

http://www.squareknot.net/suzi_prop_hub.pdf

In some cases, but not all, this bushing (often molded of rubber) will break loose from the outer prop when the prop strikes a hard object (eg, oyster shucking). (A "spun" prop) This then prevents the undue force from being transmitted to the prop drive shaft and elsewhere into the gear case (or God forbid) engine. Of course, this is not a fail safe mechanism.

Captain's Choice's experience is not that unusual. I just pulled my props (every 50-100 hours) and found about a 1/4 mile of 50 lb test wrapped around the prop collar just inside the gear case housing. (not mine - I use Fire Line.) Impossible to see from the outside (without pulling prop), but enough mono wrapped around the prop in this fashion is enough to burst the lip of the gear case housing. Bummer.

Don't know about increased incidence of collatoral damage with SS props. Some say "yes". See http://www.ankn.uaf.edu/publications/VS/lowerunit.html. The improved performance (they deform less) could be worth the risk, though. They are for sure "chick magnets"... (Or so my teenage son tells me.)
 
I still am not convinced that stainless props are much more prone to damaging lower units than aluminum. I looked at that website and am hesitant to completely accept the author as an expert on outboards when he doesn't understand the difference between ventilation and cavitation.
 
Still nothing here that would keep me from running my SS prop. I just rely on the rubber hub bushing as a "fuse". Might not work every time. But, heck, even CatDogCat's aluminum one still allowed significant damage during a prop strike.

On a couple of other threads there are discussions of ComProps simply failing without hitting anything. I think Tyboo even said he lost a blade on an aluminum prop without a prop strike. Inconvenient at best. At worst, seems like a recipe for disaster if those kinds of failures happened in bad seas close to the rocks (we all remember Murphy's Law, right?). I say go with whatever one works best. And since the SS units flex less, they transfer more power... at least I think that's the claim.

So, if you can pick up a SS prop for a song, I say go for it. :thup
 
composite props and spun props, I have stories for both. I had a comprop on my last boat and loved it. after dinging the stock honda 3 blade I switched to a comprop 4 blade. the comprop was not stiff enough when the boat was fully loaded and would "slip" when I really got on it. I changed to a 4 bladed solas prop, $ 86.00 at three rivers in woodenville, just in time for the desolation sound gig and really liked it over the comprop. I still think comprops are great for lighter boats but not a fully loaded c-dory, and I really loved the one on my last boat.

A buddy of mine built a engine for his 16ft tri-hull ski boat. the boat looked like it was going to sink at any moment. the engine was rated at 400hp. his nick name is motor head. well we took it to the river to fish stripers in the sac. when he opened it up we did not go anywhere,but if we were gentel with the throttle we moved just fine. the engine was spinning the hub. after about five open throttle starts we had to limp back to the dock. when we pulled the prop it damm near fell of the hub. the rubber was toast. after investing in a better prop, the other one was 20 years old, we were able to hit 60 mph on the river and never hit max rpm. we did hit max pucker factor first.
 
So far, the responses have been in favor of aluminum and comp props. Some sad stories and pics here. But so far, all the bent shafts, ruined props, and lower unit replacements have been achieved with other than a stainless steel prop. Lots of theory about stainless vs other materials. But of all the Brats out there, who runs stainless?

Lets hear from some of the Brats who run stainless steel props. Maybe a poll is in order.

And out of those who do run stainless, does anyone have any experience with the Michigan Match line of stainless props?

John
Swee Pea
 
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